section, a demodulator section, a baseband amplifier section, and a control section.
The components contained in the receiver's preamplifier are usually located as near the antenna as
possible to provide for maximum receiver sensitivity. The input signals are coupled directly from the antenna to
the preamplifier. The preamplifier section of the simplified receiver contains a parametric amplifier and a
a. A low noise, cryogenic parametric amplifier is used in the preamplifier to provide sufficient gain and
to insure an equivalent noise temperature of less than 200,, Kelvin for the receiver when tuned across the receive
band of frequencies. Since the parametric amplifier is the first amplifier in the receiver, it determines the noise
characteristics for the complete receiver.
b. The power requirements of the parametric amplifier's RF pump are met by an RF module (noise
source). The component in the RF module that generates the pump frequency is a klystron.
c. The low-noise wideband traveling-wave tube (TWT) provides additional amplification of the 8-GHz
The converter unit provides the first frequency conversion for the receiver. The signals applied to the
converter have a bandwidth of approximately 500 MHz. The mixer stage within the converter unit converts the 8-
GHz signals from the TWT to 1,730 MHz. The beacon signal channel can be any designated frequency within the
range from 1,230 to 2,230 MHz which results in an output bandwidth of 1 GHz. The TWT located in this unit
provides the required gain needed to offset the losses incurred in the transmission downline and the rotary joint
appearing between the antenna and the receiver.
The amplifier-converter unit performs two significant functions. The first is that of diplexing between the
beacon and communication channels; the second is that of converting the communication channel frequency to an
output frequency centered at 70 MHz with a bandwidth of 50 MHz.
a. The beacon channel part of the diplexing function is provided with a tunable preselector which can be
tuned within the frequency range of 1,230 to 2,230 MHz, which corresponds to the input operating range of the
tracking receiver. The beacon signal is applied to the tracking receiver.
b. The communication channel part of the diplexing capability is mixed with the local-oscillator
injection voltage to generate the 70-MHz IF. Feedback of the injection voltage into the beacon channel is
minimized by the isolators and the bandpass filters in the unit. The 70-MHz output is amplified by a TWT to the
level required by the communication channel. Two 70-MHz outputs are provided by the amplifier-converter unit;
one output is used as the input to the noise figure meter, and the second is fed through the receiver patch panel to
the bandpass filter.